The use of protein disulfide redox agents such as protein disulfide isomerases (PDI), and thioredoxins (TRX) for various purposes has been known for some time.
Protein disulfide redox agents catalyse the general reaction: EQU R.sub.1 --SH+R.sub.2 --SH+Enz.sub.ox .revreaction.R.sub.1 --S--S--R.sub.2 +Enz.sub.red (reaction I)
where R.sub.1 and R.sub.2 represent protein entities which are the same or different, either within the same polypeptide or in two polypeptides, Enz.sub.ox is a protein disulfide redox agent in the oxidised state, and Enz.sub.red is a protein disulfide redox agent in the reduced state. EC 5.3.4.1 refers to an enzyme capable of capable of catalysing the rearrangement of --S--S-- bonds in proteins and EC 1.6.4.4 and EC 1.8.4.2 is an example of enzymes catalysing the reaction with NAD(P)H and glutathione as a mediator, respectively.
This type of activity has been designated as protein disulfide isomerase, sulfhydryl oxidase, protein disulfide reductase, disulfide isomerase, protein disulfide transhydrogenase, and sulfhydryl oxidase.
Disulfide linkages in proteins are formed between cysteine residues and have the general function of stabilising the three dimensional structure of the proteins. They can be formed between cysteine residues of the same or different polypeptides.
Disulfide linkages are present in many types of proteins such as enzymes, structural proteins, etc. Enzymes are catalytic proteins such as proteases, amylases, etc., while structural proteins can be scleroproteins such as keratin, etc. Protein material in hair, wool, skin, leather, hides, food, fodder, stains, and human tissue contains disulfide linkages. Treatment of some of these materials with PDI and TRX, and a redox partner have been described previously.
The use of TRX for waving, straightening, removing and softening of human and animal hair was described by Pigiet et al. (EP 183506 and WO 8906122). Pigiet (U.S. Pat. No. 4,771,036) also describes the use of TRX for prevention and reversal of cataracts. Schreiber (DE 2141763 and DE 2141764) describes the use of protein disulfide transhydrogenase for changing the form of human hair. Pigiet (EP 225156) describes the use of TRX for refolding denatured proteins. Use of TRX to prevent metal catalysed oxidative damage in biological reactions is described by Pigiet et al. (EP 237189).
Toyoshima et al. (EP 277563 and EP 293793) describes the use of PDI to catalyse renaturation of proteins having reduced disulfide linkages or unnatural oxidised disulfide linkages, in particular in connection with renaturation of recombinantly produced proteins. Brockway (EP 272781), and King and Brockway (EP 276547) describe the use of PDI for reconfiguration of human hair, and for treatment of wool, respectively. Sulfhydryl oxidase for the treatment of Ultra-high temperature sterilized milk is described in U.S. Pat. No. 4,894,340, U.S. Pat. No. 4,632,905, U.S. Pat. No. 4,081,328 and U.S. Pat. No. 4,053,644. Schreiber (DE 2141763 and DE 2141764) describes the use of protein disulfide transhydrogenase for changing the form of human hair.
The uses of such enzymes have all been connected with reduction of protein disulfide linkages to free protein sulhydryl groups and/or the oxidation of protein sylfhydryl groups to protein disulfide linkages, and/or the rearrangement of disulfide linkages in the same or between different polypeptides, and sometimes to the use of these processes in sequence.
Protein disulfide redox agents can be divided into two main groups of enzymes, thioredoxin type (TRX), and protein disulfide isomerase type (PDI).
Both these can be modified to obtain protein engineered derivatives, chemical modifications and hybrids of TRX and/or PDI (ENG).
TRX is a 12-kDa protein having a redox-active disulfide/dithiol and catalysing thiol-disulfide exchange reactions (Edman et al., Nature 317:267-270, 1985; Holmgren, Ann. Rev. Biochem. 54:237-271, 1985; Holmgren, J. Biol. Chem. 264:13963-13966, 1989). PDI consists of two subunits, each consisting of two domains which are homologous to TRX.
TRX and PDI can be obtained from a number of sources: PDI: protein disulfide isomerases have mainly been identified from mammalian sources, such as Bovine (Yamauchi et al., Biochem. Biophys. Res. Commun. 146:1485-1492, 1987), Chicken (Parkkonen et al., Biochem. J. 256:1005-1011, 1988), Human (Rapilajaniemi et al. EMBO J. 6:643-649, 1987), Mouse (Gong, et al., Nucleic Acids Res. 16:1203, 1988), Rabbit (Fliegel et al., J. Biol. Chem. 265:15496-15502, 1990), and Rat (Edman et al., Nature 317:267-270, 1985). PDI has furthermore been isolated from yeast (Tachikawa et al., J. Biochem. 110:306-313).
TRX: Thioredoxin has been identified from bacteriophages, bacteria such as Escherichia coli (Wallace and Kusher, Gene 32:399-408, 1984) and Bacillus subtilis (Chen et al. J. Biol Chem. 262:8787-8798, 1987) and eukaryotes.
It would be desirable to facilitate the production of protein disulfide isomerase (PDI), to be able of producing both larger amounts of the enzyme and to produce it in a more economical manner than what is possible by the prior art methods.
Engineered variants (ENG) with improved properties for particular applications are also highly desirable and can be prepared by a variety of methods based on standard recombinant DNA technology:
1) by using site-directed or random mutagenesis to modify the genes encoding TRX or PDI in order to obtain ENG with one or few amino acid changes, PA1 2) by inhibiting or otherwise avoiding dimerisation of the subunits of PDI, thus giving rise to PDI monomers, PA1 3) by producing partial monomers of PDI or TRX, in which regions of the NH2-- or COOH termini of PDI or TRX are lacking, PA1 4) by creating hybrids of PDI, TRX and/or ENG, PA1 5) by chemically or enzymatically modifying the products of 1)-4), PA1 6) by a combination of any of 1)-5).
ENG produced according to 1) were described by Lundstrom et al. (J. Biol. Chem. 267:9047-9052, 1992) and by a combination of 3) and 5) by Pigiet (WO 8906122).
PDI, and TRX can, apart from their natural sources, be obtained by expression of recombinant DNA encoding plant, animal, human or microbial PDI, or TRX, in various hosts, such as microorganisms followed by purification of PDI, or TRX from extracts or supernatants of said host organisms. This goes also for ENG. Preparation of Trx from natural sources is described by Luthman and Holmgren (Biochem. 121:6628-6633, 1982), Wada and Buchanan (in "Thioredoxins, structure and function" (Gadal, Ed.) Editions du Centre National de la Recherche Scientifique), Porque et al. (J. Biol. Chem. 245:2362-2379, 1970) and by Laurent et al. (J. Biol. Chem. 239:3436-3445), whereas recombinant production of TRX is described by Krause et al. (J. Biol. Chem. 266:9494-9500). PDI or sulfhydryl oxidase has been prepared from natural sources by Lambert and Freedman (Biochem J. 213:225-234, 1983), Starnes et al. (U.S. Pat. No. 4,632,905) and Hammer et al. (U.S. Pat. No. 4,894,340), and by recombinant technology by among others Yamauchi et al. (Biochem. Biophys. Res. Commun. 146:1485-1492, 1987). Finally, recombinant production of an ENG is described by Lundstrom et al. (J. Biol. Chem. 267:9047-9052, 1992).